In recent years, development is seen in reducing the size, thickness, and weight of a portable information terminal such as a mobile phone, DSC (Digital Still Camera), PDA (Personal Digital Assistants), PC (Personal Computer), and the like. Therefore, a speaker unit for such a portable information terminal will be mounted in a limited space, requiring a shape corresponding to the space. Accordingly, the shape of the diaphragm employed in the speaker unit will be restricted. For example, WO 2006/082754 teaches a diaphragm of a non-circular shape having a different major axis and minor axis.